| 摘要 |
A flat major surface of a disc-shaped substrate (e.g., glass or plastic) is coated with a light-reflective layer (e.g., aluminum) which is coated with a dielectric material (e.g., silicon dioxide) highly transparent for light of a frequency supplied by a recording laser. The dielectric material is coated with a thin layer of a smooth continuous, low melting point, low thermal diffusion length metal (e.g., tellurium) absorptive for light of the frequencies supplied by the recording laser. The coating parameters are chosen to establish an anti-reflective condition for the coated record blank at the recording light frequency. The light output of the laser, which is intensity modulated in accordance with a signal to be recorded, is focused upon the coated surface of the disc as the disc is rotated. With the peak intensity of the focused light sufficient to at least cause melting of the absorptive layer, an information track is formed as a succession of spaced pits in which, the reflective layer is effectively exposed through the layer of dielectric material. For playback, light of a constant intensity is focused on the information track as the disc is rotated. During playback, the focused light is of insufficient intensity to effect melting of the remaining absorptive layer, but is of a frequency at which the undisturbed regions of the coated disc exhibit an anti-reflective condition. A photo-detector, positioned to receive light reflected from the information track as the pits pass through the path of the focused light, develops a signal representative of the recorded information. |
